Naturally occurring bitumen-containing materials such as tar sands, oil sands, bituminous sands, black shales, coal formations, and weathered hydrocarbon formations contained in sandstones and carbonates have become an attractive source of hydrocarbon recovery. Bitumen is a heavy type of crude oil that can be processed (e.g., cracked) to yield lighter hydrocarbons and other commercially useful products. Naturally occurring bitumen-containing materials typically include bitumen, water, and various mineral solids (e.g., organic solids such as coal, and/or inorganic solids such as sand, rock, silt, and clay). Accordingly, an initial step in obtaining lighter hydrocarbons and other commercially useful products from bitumen includes removing (e.g., extracting, separating, etc.) the bitumen from a naturally occurring bitumen-containing material.
An example of a conventional process for obtaining bitumen from a bitumen-containing material includes mining the bitumen-containing material, mixing the mined material with hot water and caustic to produce a slurry, screening the slurry to remove larger solid materials, diluting the screened slurry with additional hot water, and temporarily retaining the diluted slurry in a primary separation vessel (“PSV”). In the PSV, bitumen globules contact and coat air bubbles that are introduced into and/or are already entrained within the diluted slurry. The buoyant bitumen-bubble aggregates rise through the diluted slurry, along with some mineral-bubble aggregates, and form a primary bitumen froth in a top section of the PSV. Middlings comprising water and neutrally buoyant bitumen-mineral-bubble aggregates collect in a middle section of the PSV. Mineral solids not suspended within the primary bitumen froth or the middlings settle in a bottom section of the PSV. The middlings are withdrawn and treated in a series of sub-aerated, impeller-agitated floatation cells to produce a secondary bitumen froth. The primary and secondary bitumen froths are treated with solvents (e.g., naptha) and subjected to additional separation processes (e.g., centrifuging) to remove the bitumen from remaining water and mineral solids. The removed bitumen is then subjected to additional refining to produce lighter hydrocarbons and other commercially useful products. Tailings including the water and mineral solids separated during the extraction process, together with some bitumen, are sent to at least one tailings pond for long-term storage and treatment.
Unfortunately, conventional processes for obtaining bitumen from a bitumen-containing material can suffer from a variety of problems. For example, conventional processes may result in a high concentration of suspended mineral solid particles in the primary bitumen froth, middlings, and secondary bitumen froth, which can require complex, inefficient, and cost-prohibitive methods and systems to be substantially removed. In addition, the tailings produced by conventional methods may include significant amounts of bitumen, representing lost bitumen yield. Furthermore, the tailings may exhibit a sludge-like consistency that can essentially last indefinitely, and may also include hazardous materials (e.g., extraction solvents), necessitating the use of specialized and costly tailings ponds for long-term storage and treatment.
Thus, there remains a need for new, simple, and cost-efficient methods of obtaining bitumen from bitumen-containing materials that overcome one or more of the above problems.